TIME AND CHANGE 
but a small fraction of one of the daysthat make up 
the periods with which the geologist deals. And the 
span of human life, how it dwindles to a point in the 
face of the records of the rocks! Doubtless the birth 
of some of the mountain-systems of the globe is still 
going on, and we suspect it not; an elevation of one 
foot in a century would lift up the Sierra or the 
Rocky Mountains in a comparatively short geologic 
period. 
Il 
It was the geologist that emboldened Tennyson 
to sing, — 
“The hills are shadows and they flow 
From form to form and nothing stands, 
They melt like mists, the solid lands, 
Like clouds they shape themselves and go.” 
But some hills flow much faster than others. Hills 
made up of the latest or newest formations seem to 
take to themselves wings the fastest. 
The Archean hills and mountains, how slowly 
they melt away! In the Adirondacks, in northern 
New England, in the Highlands of the Hudson, they 
still hold their heads high and have something of the 
vigor of their prime. 
The most enduring rocks are the oldest; and the 
most perishable are, as a rule, the youngest. It takes 
time to season and harden the rocks, as it does men. 
Then the earlier rocks seem to have had better stuff 
in them. They are nearer the paternal granite; and 
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